This invention relates to Extremely High Frequency (EHF) and Millimeter have (MMN) amplifiers, and has particular relation to amplifier's using quasi-optical spatial power combining techniques.
FIG. 1 shows the grid amplifier disclosed in Kim etal., "A Grid Amplifier", IEEE Microwave and Guided Nave Letters, Vol. 1, No. 11, November 1991, the disclosure of which is incorporated herein by reference. Input microwaves with a vertically polarized E field pass, left to right, through an input polarizer of horizontal wires and incident on a grid amplifier. The horizontal wires affect only the non-existent horizontally polarized component of the input microwaves. The grid amplifier amplifies these input microwaves and radiates horizontally polarized output microwaves, both to the left and to the right.
The output microwaves moving to the right pass through an output polarizer of vertical wires, which have no effect on the horizontally polarized output microwaves. The (horizontally polarized) output microwaves moving to the left reflect from the horizontal wires of the input polarizer and pass through the amplifier grid unchanged; the amplifier grid detects only vertically polarized microwaves. The input polarizer is placed at a distance from the amplifier grid such that the reflected microwaves from the input polarizer combine constructively with the output microwaves propagated from the amplifier grid directly to the right. The input polarizer also prevents (or greatly reduces) feedback of the output microwaves back into the input horn (see FIG. 2). These polarizers provide the additional functions of independent tuning of the input and output circuits; that is, the act as matching impedances for the grid amplifiers.
My earlier patent, "High Efficiency Bi-Directional Spatial Power Combiner Amplifier," U.S. Pat. No. 5,214,394, issued May 25, 1993, the disclosure of which is incorporated herein by reference, uses a single horn both for input and output, as shown in FIG. 3. An ortho mode transducer or a circulator is used to isolate the output signal from the input signal. The side of the amplifier grid facing away from the input-output horn may be used to supply power and remove heat. If this approach is used for Kim's grid amplifier, the capacity to match the impedance of the horn to that of free space is lost, however, especially since required impedances may well differ for the input and output modes.